1. Field of the Invention
This invention relates to a device for improving distribution of metal deposit on a strip in its transverse direction in a continuous electroplating apparatus, and more particularly a device for preventing edges of a steel strip from being locally excessively plated in continuously feeding the strip in an electroplating apparatus.
2. Description of the Prior Art
The word "strip" used herein means steel strips and other metal strips which are relatively thin and remarkably long so as to be rolled in a coil.
The term "overcoating" used herein means locally excessive metal depositing of a plating metal on a surface to be plated.
In continuous electroplating, a traveling strip serves generally as a cathode in opposition to anodes immersed in a plating bath at its bottom to effect electrolytic action or plating during the movement of the strip. There is a general tendency of plating current to concentrate at the proximities of edges of the strip so as to cause locally excessive deposit of a plating metal thereat i.e. "edge overcoating".
In order to avoid such an edge overcoating, shielding plates made of electric insulating materials have been arranged in plating baths to partially conceal undersides of edges of strips in their longitudinal directions from the anodes. The shielding plates are positionally controlled so as to be brought into their optimum positions with the aid of signals from detectors located on one sides of the strips at entrances of the baths for detecting variation in width of the strips.
With such a control system, however, it is usually difficult to control the shielding plates with required high accuracy because of undesirable disturbance due to splashing and vaporization of the plating liquid or the like. Particularly, the shielding plates do not necessarily follow frequent movements of the edges of the strips resulting from their staggering movements and the like unavoidable in traveling, so that the shielding plates do not exhibit the expected effect preventing the edge overcoating and what is worse still they often cause another trouble "edge undercoating" which means locally insufficient metal deposit.